This invention generally relates to the field of intracorporeal catheters, and more particularly to a method of forming a distal tip on a catheter with a uniform taper and a low tip entry profile.
Percutaneous transluminal coronary angioplasty (PTCA) is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient""s coronary artery and the balloon on the catheter is inflated within the stenotic region of the patient""s artery to open up the arterial passageway and thereby increase the blood flow there through. To facilitate the advancement of the dilatation catheter into the patient""s coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery and the distal tip of the guiding catheter is then maneuvered into the ostium.
Catheters must have sufficient stiffness to be pushed through vessels as well as sufficient rigidity to provide a high degree of torsional control. However, stiffness or rigidity in the catheter tip poses the danger of puncturing or otherwise damaging a vessel lining as the catheter advances through the vascular system. It is therefore desirable for catheters to have a soft or flexible distal tip.
These types of catheters must also have an extremely small outside diameter because they are used in an intravascular environment. This is especially true of the distal tip, which has the first contact with the inner walls of the vascular system. A small outer diameter on the distal tip creates a smaller entry profile.
Therefore, what has been needed is a method to form the tips of a catheter that will improve the entry profile and have a smaller outside diameter. The present invention satisfies these and other needs.
The invention is directed to a method of forming a distal tip on a catheter. The method comprises defining an area on the distal end of a polymeric tube, creating at least one void by removing at least some of the material within the area, and sealing the void closed. The distal end has a distal tip. The area has a first location on the distal tip, a second location on the distal tip radially spaced apart from the first location, a third location proximal to the first and second locations, and a boundary including the first location, the second location and the third location. One embodiment of the invention has one area defined, while other embodiments have two or more areas defined for material removal at points about the distal tip.
In one embodiment of the invention, the polymeric tube is a catheter shaft. Specifically, a catheter distal end. The catheter distal end may be an extension of the inner member of the catheter, or an attachment that is a softer material than the majority of the material making up the catheter shaft. In some embodiments, the polymeric tube is a layered tube, with two, three, or more layers of material forming the polymeric tube. In layered embodiments, the layers preferably have compatible melting temperatures to achieve uniform and comparable taper in each layer.
In a presently preferred method, a polymeric tube is placed on a mandrel having an outer diameter equal to the desired inner diameter of the distal end. The polymeric tube will have a proximal end, a distal end with a distal tip and an inner and outer surface. The preferred embodiment of the invention then provides a cutting apparatus. Any of several cutting techniques known in the art, including but not limited to a laser, a cutting blade and a hot wire are suitable for the present method. The cutting apparatus will perform a cut on the distal end of the polymer tube. The cut will have a first location on the distal tip, a second location on the distal tip and a third location proximal to the first and second locations. The third location will be preferably spaced along the radial face between the first location and the second location. The distal end then has a cut edge that includes the first location, the second location and the third location. The cut edge may take any shape, including a U shape or a stepped shape. In a specific embodiment, the cut edge is a V shape.
Additional embodiments of the invention include removing one or multiple volumes of material from the defined area. By way of example and not as a limitation, this could be accomplished by subjecting the distal end to a laser beam. The one or multiple volumes may have any shape. Additionally, the volumes need not touch, which would leave residue material within the area.
The first location is about 0.004 inches (0.102 mm) to about 0.008 inches (0.203 mm) from the second location. In one specific embodiment, the polymeric tube is a catheter for a 0.014 inch (0.356 mm) guidewire system. The catheter has an inner diameter of 0.016 inch (0.406 mm), and an outer diameter of about 0.023 inch (0.584 mm) to about 0.025 inch (0.635 mm). For this catheter, the first location is about 0.005 inches (0.147 mm) to about 0.007 inches (0.177 mm) from the second location.
The third location is proximal to the first and second locations. The third location is typically about 0.01 inches (0.254 mm) to about 0.02 inches (0.508 mm) from the distal tip along the longitudinal axis. For the 0.014 inch (0.356 mm) guidewire system described above, the third location was about 0.013 inches (0.3302 mm) to about 0.017 inches (0.432 mm) from the distal tip.
After the area has been defined, at least a portion of the material within the area is removed from the polymeric tube. This results in a void of material on the distal end, specifically a V-shaped recess. For the 0.014 inch system described above, the removed material resulted in a V-shape area, with an angle at the proximal location of about 10 degrees to about 44 degrees.
In the V-shape cut embodiment, removing the material also results in the creation of a face between the inner surface of the polymeric tube and the outer surface at the first location and a similar face at the second location. For the purpose of this patent, this face is defined as a radial face. In certain embodiments, the radial face at the first location may have an angle of about 5 degrees to about 30 degrees with respect to the radial face at the second location. Specifically, the angle is about 10 degrees to about 20 degrees.
The tube is then sealed using a suitable method such as heat sealing. Additional sealing processes include, but are not limited to, adhesive, fusion or laser welding and heat shrinking. Laser welding and heat shrinking are preferred sealing processes.
The method of forming a distal tip of this invention provides for a distal end with a uniform taper to the distal tip. Additionally, the distal tip has a low entry profile, easing entry into the vasculature. These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.